Nitric esters and nitrate salts of specific drugs

ABSTRACT

Nitric acid salts with medicines active in the respiratory system pathology treatment.

[0001] The present invention relates to compounds, or pharmaceuticalcompositions thereof, for systemic and non systemic use, to be employedin the respiratory system pathology treatment with or without infectiveetiopathogenetic basis, specifically chronic pulmonary diseases (chronicobstructive pulmonary diseases (COPD)), such as asthma, bronchitis,enphisema, thromboembolism with lower side effects compared with thedrugs at present used for the treatment of these pathologies.

[0002] It is known in the art that for the treatment of thesepathologies the most used products are Salbutamol, Salmeterol, etc. Seefor instance the volume “Textbook of Therapeutics—Drugs and DiseaseManagement—6th Edition 1996” page 685. These products are effective buthave the drawback to give side effects in particular towards thecardiovascular apparatus. Said products must be administered withcaution to patients suffering from cardiovascular pathologies.

[0003] Other products used in these pathologies as such or ascoadjuvants of other medicines are for instance Ambroxol and Bromhexine,the administration of which is accompanied also by the presence of sideeffects for the gastrointestinal apparatus, such as burnings and gastricsensitiveness.

[0004] The need was felt to have available compounds and theirpharmaceutical compositions, effective in the treatment of respiratorysystem pathologies., combined with lower side effects for thecardiovascular apparatus and/or the gastrointestinal apparatus.

[0005] The Applicant has unexpectedly and surprisingly found specificcompounds and compositions thereof solving the above mentioned technicalproblem.

[0006] It is an object of the present invention nitrate salts ofcompounds, or their pharmaceutical compositions, to be used for thetreatment of respiratory system pathologies, specifically chronicpulmonary diseases (chronic obstructive pulmonary diseases (COPD)), suchas asthma, bronchitis, enphisema, thromboembolism, infective pulmonarydiseases, said compounds being characterized in that they contain atleast a reactive group capable to be salified with nitric acid, saidcompounds being selected from the following ones:

[0007] The preferred compounds are Salbutamol, also known as Albuterol,Cetrezin, Emedastine, Ambroxol.

[0008] The nitrate salts of the present invention can be obtained alsoby using the above mentioned compounds, which optionally contain one ormore —ONO₂ groups covalently bound to the molecule by one of thefollowing bivalent binding bridges:

[0009] YO wherein Y is a C₁-C₂₀ alkylene linear or branched whenpossible, preferably from 2 to 5 carbon atoms, or an optionallysubstituted cycloalkylene from 5 to 7 carbon atoms;

[0010] Y₁ selected from:

[0011] wherein n₃ is an integer from 0 to 3;

[0012] wherein nf′ is an integer from 1 to 6 preferably from 2 to 4;

[0013] wherein R_(1f)=H, CH₃ and nf is an integer from 1 to 6;preferably from 2 to 4.

[0014] These compounds containing a —ONO₂ group covalently bound to themolecule by means of one of the above indicated bivalent bindingbridges, are prepared as described in the patent application WO 95/30641in the name of the Applicant, herein incorporated by reference.

[0015] In the compositions according to the present invention also oneor more isomers (optical isomers included), when available, of the abovedescribed compounds, can be used.

[0016] Examples of isomers are cis-, trans-, optical isomer D and L orthe racemic, enantiomer. In general one isomeric form haas higheractivity with respect to the other, e.g. D form with respect to L formor viceversa.

[0017] The salts of the invention contain at least one nitrate ionmole/mole of the precursor. Preferably the ratio between the moles ofnitrate ion and those of the precursor is unity; salts with a highermolar ratio can be obtained when in the molecule there are other aminegroups basic enough to form a ionic bond with the nitrate anion.

[0018] The salts of the present invention are formulated in thecorresponding pharmaceutical compositions according to the knowntechniques in the field, together with the usual excipients; see forinstance the “Remington's Pharmaceutical Sciences 15a Ed.” volume.

[0019] The precursors of the salts belonging to the above mentionedclasses are prepared acording to the methods described in the MerckIndex 14a Ed., herein incorporated by reference.

[0020] The salts of the present invention are obtainable according toone of the following methods.

[0021] If the precursor to be used to form the salt according to theinvention is available as a free base, or as a corresponding salt, bothsoluble in an organic solvent preferably not containing hydroxyl groupsin the molecule, such as for example acetonitrile, ethyl acetate,tetrahydrofuran, etc., the nitrate salt is prepared by dissolving thesubstance or its salt in said solvent at a concentration preferablyequal or higher than 10% w/v, and then adding the requested amount ofconcentrated nitric acid, preferably diluted before addition in the samesolvent used formerly to dissolve the compound, preferably cooling themixture during and after said addition at temperatures between 20° C.and 0° C., recovering the obtained product by filtration and optionallywashing the solid with the same chilled solvent.

[0022] When the precursor or its available salt are slightly soluble inthe above mentioned solvent, an hydroxylated solvent is added to saidsolvent to improve solubility. Examples of such hydroxylated solvent aremethyl alcohol, ethyl alcohol and water. Precipitation can beaccellerated by diluting with an apolar solvent after nitric acidaddition.

[0023] When the precursor is salified with an hydrogen halogenide, thesalt with nitric acid can be prepared by adding silver nitrate to thesolution of the halogenide in the above solvent. After filtering offsilver halogenide, the solution is concentrated and cooled to recoverthe nitrate salt by precipitation.

[0024] Starting from a salt of the precursor wherein the anion isdifferent from chloride it is however preferable to treat an aqueoussolution of said salt with a saturated solution of carbonate orbicarbonate sodium or potassium salt, or with a sodium or potassiumhydroxide diluted solution, then extracting the aqueous phase with asuitable organic solvent (for example halogenated solvents, esters,ethers), dehydrating and then evaporating the organic solution,dissolving the thus obtained residue in the above mentioned solventswhich do not contain hydroxyl groups, e.g. acetonitrile, or in a mixtureof said solvent with an hydroxylated solvent, and then following theaforementioned described preparation methods.

[0025] The salts and compositions of the present invention can be usedfor systemic administration, for example they can be administered byoral route, such as for expectorants; by intramuscular, intravenousroute, etc.; or they can be used for non-systemic administrations, forexample as aerosols or topical applications. In general the salts of theinvention are used for the same therapeutical applications of theprecursors.

[0026] The nitrate salts of the invention have increased general safetyin the confront of the precursors.

[0027] The administered doses are those typical of the precursors;however since the products of the invention show a therapeuticeffectiveness superior to that of the precursors, they can be used alsoat doses higher than those of the precursors without giving sideeffects.

[0028] Other applications of the invention products are as tokolitics(antispasmodic), for example uterine musculature antispasmodics,intestinal musculature antispasmodics; antihistamine (antiallergics) forexample for ophtalmic applications; anticough, antibacterians forinfective respiratory diseases. They can be administered by systemic ornon systemic route, as indicated above, or also in the form ofophthalmic compositions, such as collyria, etc.

[0029] The following examples are given with the merely purpose toillustrate the invention and they are not limitative of the same.

EXAMPLE 1

[0030] Ambroxol Nitrate Salt Preparation

[0031] An Ambroxol solution (4 g, 20.6=moles) is prepared by dissolvingit in a mixture of acetonitrile (30 ml) and tetrahydrofuran (10 ml). Atlow temperature (4° C.) nitric acid diluted in acetonitrile is added(3.5 ml taken from a solution obtained by adding acetonitrile to 2.7 mlof nitric acid 65% and bringing to the final volume of 10 ml withacetonitrile). After 30 minutes ethyl ether (100 ml) is slowly added, atthe same temperature (+4° C.). A precipitate is formed which isfiltered, washed with ethyl ether and dried under vacuum. A whiteamorphous solid is obtained which by the elemental analysis results tocorrespond to the nitrate salt of Ambroxol: C H N Br Calculated 35.40%4,34% 9.53% 36.23% Found 35.37% 4.31% 9.57% 36.26%

EXAMPLE 2

[0032] Salbutamol Nitrate Salt Preparation

[0033] Starting from a Salbutamol solution (4 g, 16.7 mmoles) inacetonitrile (30 ml) and tetrahyrofuran (10 ml) and using 4 ml of nitricacid solution in acetonitrile and the same procedure of Example 1, anamorphous solid is obtained which at the elemental analysis correspondsto the nitrate salt of Salbutamol: C H N Calculated 51.65% 7.32% 9.27%found 51.54% 7.38% 9.22%

[0034] Pharmacological Tests

EXAMPLE 3

[0035] Acute Toxicity Studies of the Invention Salts

[0036] The products have been administered in suspension ofcarboxymethylcellulose 2% by weight to groups of 10 mice each

[0037] The salt acute toxicity was evaluated by oral administration ofsingle doses of the compounds to groups of 10 rats each, increased up to100 mg/Kg.

[0038] The animals were kept under observation for 14 days, recordingthe lethality incidence and the appearance of toxic symptoms.

[0039] Also after administering of a dose of 100 mg/kg no sign ofapparent toxicity has been noted.

EXAMPLE 4

[0040] Study of the Salbutamol and Nitrate Salbutamol Effects on theExperimental Bronchoconstriction in the Guinea Pig

[0041] The animals were prepared according to the method of Del Soldatoet Al., J. Pharmacol. Methods 5 279 1981 for the cardiorespiratoryactivity surveying. Each groups consisted of eight animals. 0.1 ml of acapsaicin saline solution (1 μg/Kg) was injected by intravenous route tothe animals. For a total 15 minutes, starting from 5 minutes beforecapsaicin injection to 10 minutes after) Salbutamol (0.3 nmoles/min), orthe corresponding nitrate salt (0.3 nmoles/min) or only the carrier wereadministered by intravenous infusion were administered to each group.

[0042] The tidal air variation before and after the capsaicinadministration was measured by a Konzett apparatus modified as describedin the above mentioned Del Soldato reference, connected to a polygraphicsystem.

[0043] The heart frequency was determined by an electrocardiographicdevice, according to the usual methods. The results are reported inTable 1. The average value of the heart frequency followingadministration of the vehicle was of 188±7 beats per minute. Theresponses are expressed as percent values with respect to the control.

[0044] As indicated in Table I, the Salbutamol nitrate salts results aseffective as Salbutamol in inhibiting the bronchoconstrictive responseinduced by capsaicin, but the salt is better tolerated (no tachycardiacresponse) with respect to Salbutamol. TABLE I BronchoconstrictionTachycardia Treatment (%) (%) Carrier 100 100 Salbutamol.HNO₃ 0 97Salbutamol 0 116

EXAMPLE 5

[0045] Cetirizine Nitrate Salt Preparation

[0046] The salt is prepared by adding to a solution of Cetirizine (2 g,5.14 mmoles) in a solvent mixture made of acetonitrile (10 ml) andtetrahydrofuran (5 ml), 1.23 ml of the solution of nitric acid inacetonitrile described in example 1. An amorphous solid is obtainedwhich at the elemental analysis corresponds to the nitrate salt ofCetirizine: C H N Cl Calculated 55.81% 5.79% 9.29% 7.84% found 55.84%5.75% 9.22% 7.83%

EXAMPLE 6

[0047] Loratidine Nitrate Salt Preparation

[0048] The salt is prepared by adding to a solution of Loratidine (1 g,2.61 mmoles) in a solvent mixture made of acetonitrile (7 ml) andtetrahydrofuran (3 ml), 0.63 ml of the solution of nitric acid inacetonitrile described in example 1. The solid obtained at the elementalanalysis corresponds to the nitrate salt of Loratidine: C H N ClCalculated 59.26% 5.42% 9.42% 7.95% Found 59.24% 5.38% 9.42% 7.93%

EXAMPLE 7

[0049] Terfenadine Nitrate Salt Preparation

[0050] The salt is prepared by adding to a solution of Terfenadine (1.5g, 3.18 mmoles) in a solvent mixture made of acetonitrile (15 ml) andtetrahydrofuran (5 ml), 0.76 ml of a solution of nitric acid inacetonitrile as described in example 1. The solid obtained at theelemental analysis corresponds to the nitrate salt of Terfenadine: C H NCalculated 71.88% 7.91% 5.23% found 71.90% 7.88% 5.24%

EXAMPLE 8

[0051] Emedastine Nitrate Salt Preparation

[0052] The salt is prepared by adding to a solution of Emedastine (2 g,5.47 mmoles) in a solvent mixture made of acetonitrile (10 ml) andtetrahydrofuran (7 ml), 0.7 ml of the solution of nitric acid inacetonitrile described in example 1. The solid obtained at the elementalanalysis corresponds to the nitrate salt of Emedastine: C H N Calculated55.87% 7.44% 19.15% Found 55.84% 7.43% 19.18%

EXAMPLE 9

[0053] Bromhexine Nitrate Salt Preparation

[0054] The salt is prepared by adding to a solution of Bromhexine (2 g,5.17 mmoles) in a solvent mixture made of acetonitrile (10 ml) andtetrahydrofuran (10 ml), 1.24 ml of the solution of nitric acid inacetonitrile described in example 1. The solid obtained at the elementalanalysis corresponds to the nitrate salt of Bromhexine: C H N BrCalculated 38.29% 4.81% 12.75% 36.39% Found 38.31% 4.84% 12.77% 36.41%

EXAMPLE 10

[0055] Dextromethorphan Nitrate Salt Preparation

[0056] The salt is prepared by adding silver nitrate (0.96 g, 5.68mmoles) to a solution of Dextromethorphan hydrobromide (2 g, 5.68mmoles) in acetonitrile (20 ml). The solution is then stirred at roomtemperature for 30 minutes. Filtering is then effected to remove silverbromide precipitate. The clear solution is added of ethyl ether (110ml). A precipitate is formed, that is filtered, washed with ethyl etherand dried under vacuum. The solid obtained at the elemental analysiscorresponds to the nitrate salt of Dextromethorphan: C H N Calculated64.65% 7.83% 12.56% Found 64.68% 7.85% 12.54%

EXAMPLE 11

[0057] Ketotifen Nitrate Salt Preparation

[0058] The salt is prepared by adding to a solution of Ketotifen (1 g,3.23 mmoles) in a solvent mixture made of acetonitrile (10 ml) andtetrahydrofuran (5 ml), 0.78 ml of the solution of nitric acid inacetonitrile described in example 1. The solid obtained at the elementalanalysis corresponds to the nitrate salt of Ketotifen: C H N SCalculated 61.27% 5.40% 11.28% 8.61% Found 61.24% 5.43% 11.27% 8.60%

EXAMPLE 12

[0059] Nedocromil Nitrate Salt Preparation

[0060] The salt is prepared by adding to a solution of Nedocromil (1 g,2.69 mmoles) in a solvent mixture made of acetonitrile (7 ml) andtetrahydrofuran (5 ml), 0.64 ml of the solution of nitric acid inacetonitrile as described in example 1. The solid obtained at theelemental analysis corresponds to the nitrate salt of Nedocromil: C H NCalculated 52.54% 4.17% 9.67% Found 52.56% 4.19% 9.63%

EXAMPLE 13

[0061] Dextrorphan Nitrate Salt Preparation

[0062] The salt is prepared by adding silver nitrate (0.50 g, 2.96mmoles) to a solution of Dextrorphan hydrobromide (1 g, 2.96 mmoles) inacetonitrile (17 ml). The solution is then stirred at room temperaturefor 30 minutes. Filtering is then effected to remove silver bromideprecipitate. The clear solution is added of ethyl ether (100 ml). Aprecipitate is formed, that is filtered, washed with ethyl ether anddried under vacuum. The solid obtained at the elemental analysiscorresponds to the nitrate salt of Dextrorphan: C H N Calculated 63.73%7.54% 13.11% Found 63.71% 7.55% 13.10%

[0063] Pharmacological Tests

EXAMPLE 14

[0064] Antihistaminic activity in the Guinea Pig of Cetirizine Nitrateand Cetirizine Hydrochloride—Studies on the ExperimentalBronchoconstriction

[0065] The animals were prepared according to the method of Del Soldatoet Al., J. Pharmacol. Methods 5 279 1981 for the cardiorespiratoryactivity surveying. 0.1 ml of a histamine saline solution (2 μg/Kg) wasinjected by intravenous route to the animals. Three groups were formed,each group consisting of 8 animals. Cetirizine nitrate, Cetirizinehydrochloride, or the vehicle alone, were administered endovenously at adose of 77 μmoles/μg

[0066] The tidal air variation before and after the capsaicinadministration was measured by a Konzett apparatus modified as describedin the above mentioned Del Soldato reference, connected to a polygraphicsystem.

[0067] In following Table II the animal response for each treated groupare expressed as percent values with respect to the control.

[0068] As indicated in the Table, the nitrate salt of Cetirizinepossesses an improved antihistamine activity in the confront ofCetirizine hydrochloride. TABLE II Broncocostriction Treatment (%)Vehicle 100 Cetirizine nitrate 0 Cetirizine hydrochloride 40

EXAMPLE 15

[0069] Anti-Tussive Activity in the Guinea Pig of DextromethorphanHydrochloride, Dextromethorphan Nitrate, Dextrorphan Hydrochloride andDextrorphan Nitrate

[0070] Guinea pigs (weight: 430+20) were treated as described by Bragaet Al. Arzneim. Forsch./Drug Res. 43, 550, 1993.

[0071] In this pharmacological experiment 5 groups of 8 animals eachwere formed. One group was not treated and was the control group.

[0072] Each animal was placed in a cilindrical glass container havingone tubing through each of the two circular flat surfaces. Said tubingwere, respectively, for the aerosol inlet and outlet. The outlet tubingis connected to a polygraphic system.

[0073] The aerosol was formed from a solution 7.5 W by weight of citricacid in water.

[0074] The air variation inside the glass container was registeredbefore and after a cough stroke caused by the aerosol. One hour laterDextromethorphan hydrochloride, Dextromethorphan nitrate, Dextrorphanhydrochloride and dextrorphan nitrate were i.p. administered in aphysiologic solution at a dose of 110 micromoles/Kg. 30 minutes afterthe injection the animals were treated with the aerosol. It was thenregistered the number of cough strokes for a time of 10 minutes. In thefollowing Table III are reported the average response obtained from eachtreated group, referred to that of the control group, made 100 W. TABLEIII cough strokes Treatment (%) Vehicle 100 Dextromethorphan nitrate 0Dextromethorphan hydrochloride 30 Dextrorphan nitrate 0 Dextrorphanhydrochloride 40

[0075] As shown in the Table, the nitrate salts of Dextromethorphan andDextrorphan are more potent antitussive agents than the correspondinghydrochlorides.

EXAMPLE 16

[0076] Mucolitic Activity in Mice of Ambroxol Nitrate and AmbroxolHydrochloride

[0077] Mucolitic activity in male mice was evaluated according to theMethod of Engler and Zselenyi, J. Pharm. Methods 11, 151, 1984. By thismethod it is determined the quantity of phenol red in the trachealsecretion. The animals were previously administered i.p. at a dose of500 mg/Kg with the dye dissolved in physiologic solution. 3 groups ofmice (weight 18±2 g), of 10 animal each, were treated i.p. with the dye.One group was the control group. Each of the two treated groupsreceived, ten minutes before the above injection, an i.p. injection of264 micromoles/Kg of Ambroxol nitrate or Ambroxol hydrochloride,respectively. 30 minutes after the phenol red injection, the animalswere sacrificed. The trachea was freed from the sorrounding tissues,dissected and washed for 30 minutes in 3 ml of physiologic solution. 0.1ml of 1 M sodium hydroxyde were then added to the physiologic solution.The washings were centrifuged for 15 minutes at 3000 rpm. Aspectrophotometric assay was performed on the supernatant in order todetermine the concentration of phenol red in the physiologic solution.Mucolitic activity was determined as % variation of absorbance of thesample in the confront of that of the control group, assumed to be 100%.

[0078] Table IV resumes the results obtained. TABLE IV Mucoliticactivity Treatment (%) Vehicle 100 Ambroxol nitrate 0 Ambroxolhydrochloride 30

[0079] The table shows that the mucolitic activity of the Ambroxolnitrate salt is higher than that of the corresponding hydrochloride.

EXAMPLE 17

[0080] Metronidazole Nitrate Salt Preparation

[0081] The salt is prepared by adding to a solution of Metronidazole (1g, 5.84 mmoles) in a solvent mixture made of acetonitrile (8 ml) andtetrahydrofuran (5 ml), 1.40 ml of the solution of nitric acid inacetonitrile described in example 1. The solid obtained at the elementalanalysis corresponds to the nitrate salt of Metronidazole: C H NCalculated 30.77% 4.30% 24.03% Found 30.74% 4.28% 24.00%

EXAMPLE 18

[0082] Isoniazid Nitrate Salt Preparation

[0083] The salt is prepared by adding to a solution of Isoniazid (2 g,14.58 mmoles) in a solvent mixture made of acetonitrile (20 ml) andtetrahydrofuran (10 ml), 3.50 ml of the solution of nitric acid inacetonitrile described in example 1. The solid obtained at the elementalanalysis corresponds to the nitrate salt of Isoniazid: C H N Calculated36.00% 4.02% 27.99% Found 35.97% 4.00% 28.01%

EXAMPLE 19

[0084] Erythromycin Nitrate Salt Preparation

[0085] The salt is prepared by adding to a solution of Erythromycin (2g, 2.72 mmoles) in a solvent mixture made of acetonitrile (23 ml) andtetrahydrofuran (17 ml), 0.65 ml of the solution of nitric acid inacetonitrile described in example 1. The solid obtained at the elementalanalysis corresponds to the nitrate salt of Erythromycin: C H NCalculated 57.72% 8.89% 3.63% Found 57.75% 8.90% 3.65%

EXAMPLE 20

[0086] Acyclovir Nitrate Salt Preparation

[0087] The salt is prepared by adding to a solution of Acyclovir (1 g,4.44 mmoles) in a solvent mixture made of acetonitrile (10 ml) andtetrahydrofuran (10 ml), 1.06 ml of the solution of nitric acid inacetonitrile described in example 1. The solid obtained at the elementalanalysis corresponds to the nitrate salt of Acyclovir: C H N Calculated33.33% 4.19% 29.17% Found 33.30% 4.20% 29.18%

EXAMPLE 21

[0088] Pyrazinamide Nitrate Salt Preparation

[0089] The salt is prepared by adding to a solution of Pyrazinamide (1g, 8.12 mmoles) in a solvent mixture made of acetonitrile (10 ml) andtetrahydrofuran (10 ml), 1.95 ml of the solution of nitric acid inacetonitrile described in example 1. The solid obtained at the elementalanalysis corresponds to the nitrate salt of Pyrazinamide: C H NCalculated 48.78% 3.25% 30.10% Found 48.80% 3.24% 30.13%

1. Nitrate salts of compounds selected from the following ones:


2. Nitrate salts according to claim 1 wherein the compounds areSalbutamol Cetrezin Emedastine, Ambroxol.
 3. Nitrate salts according toclaims 1-2, wherein the compounds contain one or more —ONO₂ groupscovalently bound to the molecule by one of the following bivalentbinding bridges: YO wherein Y is a C₁-C₂₀ alkylene linear or branchedwhen possible, preferably from 2 to 5 carbon atoms, or a cycloalkylenefrom 5 to 7 carbon atoms optionally substituted; Y₁ selected from:

wherein n₃ is an integer from 0 to 3;

wherein nf′ is an integer from 1 to 6 preferably from 2 to 4;

wherein R_(1f)=H, CH₃ and nf is an integer from 1 to 6; preferably from2 to
 4. 4. Nitrate salts according to claims 1-3 containing one or moreisomers of the indicated compounds.
 5. Nitrate salts according to claims1-4, wherein the salts of said compounds contain at least one molenitrate ion/mole of the compound.
 6. Pharmaceutical compositions of thenitrate salts according to claims 1-5.
 7. Nitrate salts andpharmaceutical compositions according to claims 1-6 for use asmedicines.
 8. Use of salts and compositions according to claim 7 and ofthe following compounds:

for the preparation of medicines for the treatment of respiratory systempathologies.
 9. Use of salts and compositions according to claim 7 forthe preparation of medicines for use as tokolitics.
 10. Use of salts andcompositions according to claim 7 for the preparation of medicines foruse as antiallergics, preferably for eye applications.
 11. Compoundsaccording to claim 1 having formula (I), (II), (III), (VII), (VIII),(XI) containing one or more —ONO₂ groups covalently bound to themolecule by one of the following bivalent binding bridges: YO wherein Yis a C₁-C₂₀ alkylene linear or branched when possible, preferably from 2to 5 carbon atoms, or an optionally substituted cycloalkylene from 5 to7 carbon atoms; Y₁ selected from:

wherein n₃ is an integer from 0 to 3;

wherein nf′ is an integer from 1 to 6 preferably from to 4;

wherein R_(1f)=H, CH₃ and nf is an integer from 1 to 6; preferably from2 to 4.